Several systems designed specifically to set the cervical column from behind are currently known. The conventional systems, being a part of the prior art, could be divided into the five types listed below:
Wires passing through holes made on the rear arch of each vertebra to be fixed, that are then knotted to form a lacing that joins the vertebrae to one another. It is inconvenient in that the resulting set is not sufficiently solid and, if the wires are passed beneath the laminae, manipulation can prove dangerous. PA1 Longitudinal bars joined to the vertebrae by means of wires passing beneath the rear arch laminae and then knotted around the bar. It is inconvenient in that the wires must pass beneath the laminae and this is dangerous. PA1 Hooks catching hold of the vertebral laminae and then being joined to each other by bars or screws. The Halifax system is inconvenient in that it is only useful to join two levels. The bar and hook systems can only catch hold of the two end vertebrae and not the intermediate vertebrae. They cannot be used after laminectomy. PA1 Plates fixed to the vertebrae with screws that catch hold of the articular mass of each vertebra. It is inconvenient in that the plates, being rigid, predetermined and conditions the place at which screws are inserted. PA1 The Magerl system combines the previous two systems and has a sublaminar hook and a plate, joined to the hook, that is screwed to one or two articular masses. It is inconvenient in that being a rigid part, the position of the screws is predetermined and is further only useful to join two or three levels. PA1 Possibility of being used to join all the required levels. PA1 Because it is jointed, neither the point of insertion of the screws nor the position of the hooks are predetermined, eliminating risks and expediting the placement and adaptation of the system to the morphology of the column. PA1 Having screws and hooks, it can also be used after laminectomy.